JP7213444B2 - Thermal oxidation test equipment for jet fuel - Google Patents

Description

TECHNICAL FIELD This disclosure relates to jet fuel thermal oxidation testing and, more particularly, to apparatus that can be used with jet fuel thermal oxidation test rigs to improve accuracy, efficiency, and reliability.

This application is a PCT international application claiming priority from U.S. Patent Application No. 15/826,272, filed November 29, 2017, which is hereby incorporated by reference in its entirety.

Modern jet engine systems consist of gas turbine engines running on jet fuel. Under normal operating conditions, jet fuel is heated by hot components or portions of a gas turbine engine, such as fuel nozzles, fuel nozzle support mechanisms, heat exchangers, and the like. Modern jet engine systems utilize jet fuel's ability as a heat sink to cool various aircraft systems, such as hydraulic, electronic, and lubrication systems. However, thermal management, and thus jet engine system and airframe performance, is a sensitive tradeoff between (i) running fuel system cooling and the performance, cost, and weight sacrifices of air cooling; Balance, or (ii) strikes a delicate balance between running the system as hot as possible and causing problems with unacceptable heat build-up rates. Therefore, engineers often design jet engine systems to take full advantage of the thermal stability of currently available fuels.

The trend toward increased overall engine system performance and increased airframe and engine heat loads, coupled with the concomitant trend toward reduced fuel consumption, is forcing fuel system temperatures to rise even further. Therefore, many modern high performance jet engine systems use fuel that has been subjected to thermal stress. However, at high temperatures, less stable species in jet fuel subjected to thermal stress can undergo oxidation reactions to produce gummy, gluey, granular, and coking deposits. This can lead to a variety of problems, such as clogged filters, reduced efficiency of heat exchangers, sticking or hysteresis of sliding components in control units, fouling of injectors, and distorted spray patterns. For example, the oxidation of jet fuel under thermal stress produces deposits or particles that block engine fuel nozzles, thereby causing damage to engine hot sections, particularly the combustor region, through distorted fuel spray patterns. obtain. Therefore, jet fuel thermal stability is critical to achieving optimum performance in modern gas turbine engines.

The current standard for evaluating the thermal oxidation of jet fuel is the "Standard Test Method for the Thermal Oxidative Stability of Aircraft Turbine Fuels" established by the American Society for Testing and Materials International ("ASTM International"), which states: Numbers D3241 and IP323 are given. This test method simulates the thermal stress conditions that jet fuel is exposed to during operation, and although it was developed in the early 1970s, it remains the best method for assessing the thermal stability of jet fuel. continuing. More specifically, the D3241 test method establishes a procedure for evaluating the propensity of jet fuel to deposit decomposition products in the fuel system. The D3241 test method is performed in two phases. The first phase simulates fuel conditions induced during operation of an aircraft engine, and the second phase quantifies the thermal oxide deposits formed during the first phase.

Since then, various experimental devices known as rigs have been developed to facilitate testing of D3241. These rigs are equipped with aluminum heated tubes for sampling jet fuel under conditions simulating those encountered during actual engine operation.

However, these rigs are difficult to use and require considerable expertise when installing the heating tube inside the measuring section and preparing the jet fuel sample. Additionally, these existing rigs include a pump system to deliver the fuel sample to the measurement station, which often suffers from leaks, flow variations, micro-interruptions in flow, and is expensive to operate and maintain. . Additionally, these existing rigs are equipped with outdated temperature control systems that affect test results and their reproducibility.

According to the present disclosure, a gauge is provided for positioning the heating tube within the sleeve. The gauge may include a body having first and second ends and a bore extending from the first end into the body interior a predetermined length, the bore extending into the open end of the sleeve. The heating tube has a diameter sized to receive a portion and includes a pair of shoulders flanking the reduced diameter portion. A pair of shoulders extend from the lip away from the reduced diameter portion, with one shoulder extending through the sleeve such that the lip is positioned proximate the outlet of the sleeve. extends along the length of the

In some embodiments, the gauge bore may extend from the first end a predetermined length shorter than the body. In some embodiments, a portion of the bore proximate the first end of the body may be threaded.

In some embodiments, the gauge may further include a shoulder radially disposed along the bore at a distance equal to the length from the first end. In such examples, the hole may extend from the first end to the second end of the body.

Also according to the present disclosure, a system is provided for automatically aerating a fuel sample. The system may include a pump for facilitating the airflow, a flow meter to measure the airflow, and a sample container into which the airflow is injected, the pump being further associated with the flowmeter and automated via a control loop. A controller is provided to maintain the airflow at a constant rate.

In some embodiments, the constant flow rate is 1.5 liters/minute. In some embodiments, the sample container can further include a diffuser disposed therein. In some embodiments, the system may further include a filter that filters the airflow prior to passing through the pump.

In some embodiments, the system may further include an air desiccant to remove moisture from the airflow. In such examples, the system may further include a humidity sensor positioned to sample the airflow past the air desiccant.

Also according to the present disclosure, a pump system is provided for conveying the fuel sample through the thermal oxidation rig. The pump system may include first and second syringe assemblies, each syringe assembly comprising: a hollow barrel defining a volume for holding a fuel sample; a tip located at the upper end of the barrel; With an open end located at the lower end, each syringe assembly has an inlet valve and an outlet valve. The pump system may also include a pair of pistons each arranged to slide within one of the barrel volumes, each piston extending into the volume through the open end of the barrel and through the barrel. has a shaft connected to the head portion which abuts the inner wall of the hollow barrel so as to seal the volume against the open end of the barrel. Further, the pump system may include a pair of motors, each motor engaged by one piston and independently controlled to maintain a constant flow rate of the fuel sample; The stroke of each piston is controlled so that the pistons accelerate and decelerate simultaneously.

In some embodiments, the pump system may further include a common inlet line for feeding both the inlet valve of the first syringe assembly and the inlet valve of the second syringe assembly. In these examples, the common inlet line may be connected to a sample container holding a fuel sample.

In some embodiments, the pump system may further include a common outlet line for receiving from both the outlet valve of the first syringe assembly and the outlet valve of the second syringe assembly. In these examples, fuel samples may be conveyed through a common exit line at a constant flow rate.

In some embodiments, the pump system may further include a pair of ball screw transmissions, each ball screw transmission interposed between a respective motor and the piston.

Also according to the present disclosure, a temperature system is provided for independently controlling the temperature of the busbars to improve the thermal profile of the heating tubes in the thermal oxidation rig. The thermal system may include a heat sink located proximate the base of the busbar that secures the busbar to the thermal oxidation rig. The temperature system may also include a cooling element interposed between the heat sink and the base of the busbar. The temperature system may also include forced convection devices. The temperature system may also include a thermocouple positioned at the end of the busbar opposite the base, proximate the heating tube, the thermocouple measuring the temperature of the busbar. The temperature system may also include a controller associated with the cooling element and the forced convection device, the controller controlling the cooling element and the forced convection device based on the temperature measured by the thermocouple. In some embodiments, the busbar may include holes extending from the base that receive the heat pipes.

Additionally, according to the present disclosure, a clamping system is provided for securing the heating tubes to the busbars of a thermal oxidation rig. The clamping system may include a hole extending toward the end of the busbar and terminating on the inner surface of the busbar. The clamping system may also include a pair of projections extending from the inner surface of the busbar to the ends, the projections defining a gap extending with the hole. The clamping system may also include a plate arranged to slide axially within the gap and a screw disposed within the hole and engaged with the plate, wherein rotation of the screw translates into axial displacement of the plate. be done.

The following figures are included to illustrate certain aspects of the disclosure and should not be considered as exclusive embodiments. The disclosed subject matter is capable of commensurate modifications, alterations, combinations, and equivalents in form and function without departing from the scope of the present disclosure.

1A is a perspective view of an exemplary rig that may incorporate principles of the present disclosure; FIG. 1B is a detailed perspective view of the exemplary rig of FIG. 1A showing an exemplary measurement section that may incorporate principles of the present disclosure; FIG. FIG. 2 is a side view of an exploded measuring section utilized in the rig of FIG. 1B; FIG. 3A is a detailed side view of the sleeve and heating tube assembly utilized in the measurement section of FIG. 1B, showing the fuel outlet when the heating tube is positioned within the sleeve. 3B is a cross-sectional side view of the fuel outlet of FIG. 3A. Figures 4A and 4B are side views of the sleeve and heating tube assembly of Figure 3A showing how the gauge is used to position the heating tube within the sleeve. FIG. 4C is a cross-sectional side view of the gauge of FIGS. 4A and 4B, which may be used to position the heating tube within the sleeve. FIG. 5 is a schematic diagram showing various functions of the rig of FIG. 1A utilized for aerating fuel samples. FIG. 6A shows an exemplary operation of the manual fuel sample aeration procedure. FIG. 6B shows an exemplary operation of the automatic fuel sample aeration procedure. FIG. 7 is a schematic diagram illustrating exemplary operation of a pump system having a pair of syringe configurations. FIG. 8 is a diagram illustrating the operation of the heating system utilized in the rig of FIG. 1A; 9A is a diagram illustrating the operation of the busbar cooling system utilized in the rig of FIG. 1A; FIG. FIG. 9B is a schematic diagram of the busbar cooling system of FIG. 9A. FIG. 10 is a schematic diagram illustrating exemplary operation of a busbar cooling system that independently controls individual busbars. FIG. 11A is a schematic diagram showing a clamping system that may be utilized to secure the sleeve and heating tube assembly to the busbar, such as in the lower busbar of FIG. 1B. FIG. 11B is a schematic diagram showing an alternative clamping system that may be utilized to secure the sleeve and heating tube assembly to the busbar.

Embodiments described herein provide a positioning gauge for positioning the heating tube within the sleeve of the rig measurement section. Other embodiments described herein provide an air control system that uses automatic airflow control to provide automatic aeration of the fuel sample. Additionally, embodiments described herein provide a pump system having a paired syringe configuration. Additionally, the embodiments described herein provide a cooling system that independently controls individual busbars.

The ASTM International Jet Fuel Thermal Oxidation Test (D3241, IP323) Standard Test Method (hereinafter "Test Method") is performed in two phases. The first phase simulates fuel conditions induced during operation of an aircraft engine, and the second phase quantifies the thermal oxide deposits formed during the first phase. A technician performs the first phase through a device that simulates conditions that occur in the fuel system of an operating gas turbine engine. The apparatus, referred to herein as a rig, includes a measurement section that holds the test coupons and generally comprises a shell and tube heat exchanger that directs the fuel flow over the test coupons. The second phase consists of inspection of the test coupons either by an instrument that measures the thickness of the thermal oxide deposits at the atomic level or by visual inspection. The following disclosure focuses primarily on the first phase of the test method and the rigs used in the first phase to form thermal oxide deposits.

FIG. 1A is a partial perspective view of an exemplary rig 100 that may incorporate principles of the present disclosure. The depicted rig 100 is but one example of a test rig that can suitably incorporate the principles of the present disclosure. Indeed, many alternative designs and configurations of rig 100 may be employed without departing from the scope of this disclosure.

In the illustrated embodiment, rig 100 is configured to automatically perform the test method. However, it can also be configured to automatically run other petroleum product tests such as ISO 6249. As shown, the rig 100 includes a sample container 102, a waste container 104, and a measurement section 110 fluidly interconnecting the sample container 102 and the waste container 104 as described below. In use, a technician places a jet fuel sample S in the sample container 102 and activates the rig 100 to perform the test method, which causes the rig 100 to pump the jet fuel sample S from the sample container 102 through the measurement section 110 . , is pumped into the waste container 104 upon completion of the test method.

FIG. 1B is a detailed view of measurement portion 110 of FIG. 1A, in accordance with one or more embodiments. As shown, the measurement portion 110 can include a sleeve 112 with a heating tube 114 hermetically sealed therein (partially hidden from view in FIG. 1B). Here, the heating tube 114 is secured within the sleeve 112 via a pair of nut assemblies 136a, 136b, although other assemblies may be utilized to secure the heating tube 114 to the sleeve without departing from this disclosure. 112 may be fixed. The sleeve 112 is hollow and (although hidden from view in FIG. 1B) is open at each of its ends 112a, 112b. The measuring portion 110 also includes a fuel inlet 116 and an outlet 118 located on the sleeve 112 between the open ends 112a, 112b. Fuel inlet 116 is fluidly connected to sample container 102 and fuel outlet 118 is fluidly connected to waste container 104 . In addition, the measurement portion 110 includes a test filter 120 that is positioned adjacent the fuel outlet 118 and positioned between the fuel outlet 118 and the waste container 104 .

FIG. 1B also illustrates rig 100 with a pair of jaws or bus bars 122a, 122b arranged to secure measuring portion 110 in a desired orientation via a clamping system further described below with reference to FIG. 11A. It is a figure showing. However, alternative clamping systems may be utilized, for example as described with reference to FIG. 11B. As described below, bus bars 122a, 122b provide controlled high amperage, low voltage electrical current to heating tube 114, thereby enabling maintenance of precise temperatures during test methods. As such, the busbars 122a, 122b are directly or indirectly connected to a transformer or other power source (not shown). In some embodiments, busbars 122a, 122b are made of brass or other material that has a lower thermal conductivity than the material of heating tube 114, as described below. Additionally, thermocouple 124 is configured to provide a temperature measurement of measurement portion 110, as described below.

FIG. 2 shows a side view of measurement portion 110 when disassembled and removed from rig 100 . As shown, the sleeve 112 is hollow and the fuel inlet 116 and fuel outlet 118 are open so as to be in fluid communication with each other at the fuel inlet 116, the fuel outlet 118, and the open ends 112a, 112b. 112a and 112b. FIG. 2 also shows heating tube 114 when withdrawn from sleeve 112, which can occur before and after the test method. As shown, the heating tube 114 includes a reduced diameter portion 130 sandwiched between a pair of shoulders 132a, 132b located at opposite ends 134a, 134b of the heating tube 114. As shown in FIG. In operation, the heating tube 114 is inserted into the sleeve 112 and secured to the sleeve 112 through a pair of clamping nut assemblies 136a, 136b so that a technician can, for example, before and after performing a test method. Allows the heating tube 114 to be removed from the sleeve 112 . In the illustrated embodiment, clamping nut assemblies 136a, 136b each secure shoulder 132a of heating tube 114 at open end 112a of sleeve 112 and shoulder 132b at open end 112b. Includes gaskets, washers, seals and nuts for However, it will be appreciated that the nut assemblies 136a, 136b may be configured differently using the same and/or different components without departing from this disclosure.

The heating tube 114 also includes a thermocouple (hidden from view of the drawing) located within its interior volume, the heating tube 114 connecting the appropriate one of the pair of shoulders 132a, 132b of the heating tube 114 to each other. It is resistively heated by conductance through a pair of clamping busbars 122a, 122b. In some embodiments, the heated tube 114 is an aluminum (or other metal) coupon controlled at a high temperature by bus bars 122a, 122b, onto which the fuel sample S is pumped.

As noted above, at various times before, during, and after the test method, the technician may need to assemble or disassemble sleeve 112 and heating tube 114 . For example, the test method may require that the technician correctly assemble the measuring portion 110 (ie, install the heating tube 114 inside the sleeve 112 in a leak-tight manner) and/or test before starting the test method. After completing the procedure, the technician may require the measurement unit 110 to be disassembled. Additionally, the test method may require the technician to clean, rinse, and dry certain components during the disassembly phase. Accurate analysis and test method results depend on proper assembly, disassembly, cleaning, rinsing and drying of test method components. Proper execution of these phases of the test method therefore requires a high degree of technical expertise and can consume considerable time and resources.

3A and 3B show side views of heating tube 114 assembled within sleeve 112 and secured therein via clamping nut assemblies 136a, 136b. The test method dictates that a technician should manually place the heating tube 114 into the measuring section 110 . More specifically, the test method is such that the heating tube 114 is correctly positioned with respect to the sleeve 112 such that the lip 302 of the upper shoulder 132a (of the heating tube 114) is It stipulates that the fuel outlet 118 should be visually adjusted so that it is centered inside the opening 304 . This configuration allows the fuel sample S to flow through the fuel outlet 118 to other downstream equipment, such as differential pressure measuring equipment as described below.

Once the lip 302 of the upper shoulder 132a is centered inside the fuel outlet 118, the technician tightens and secures the heating tube 114 within the sleeve 112, eg, via nut assemblies 136a, 136b. Clamping the heating tube 114 within the sleeve 112 helps to seal the interior volume through which the fuel sample S flows, but the resulting clamping force often causes an unintended displacement of the heating tube 114 against the sleeve 112 . This causes misalignment and prevents lip portion 302 from maintaining the proper alignment described above. As a result, very fine adjustments are required to pre-position the lip 302 of the heating tube 114 to account for or anticipate such displacement during tightening. Accordingly, a technician requires a high degree of expertise to properly install heating tube 114 within sleeve 112 .

4A and 4B illustrate a positioning gauge or gauge 402 that can be utilized to positively position heating tube 114 relative to sleeve 112, according to one or more embodiments. Gauge 402 may also be provided as an accessory to assist technicians who may be forced to visually confirm the position of lip 302 within fuel outlet 118 to prime measurement station 110 . good. In the illustrated embodiment, the gauge 402 is open at its first end 404 and a hole 406 inside the first end 404 accommodates the gauge 402 at an end of the sleeve 112, e.g., the open end. It is threaded so that it can be screwed from above a plurality of screws 408 located on 112a. In some embodiments, the gauge 402 is open at its second end and includes a threaded hole in said second end that includes similarly or differently arranged screws. and such a configuration may provide the gauge 402 with the ability to be used with a variety of measurement portions 110 . The body of gauge 402 includes a central bore extending longitudinally through the body, the length over which the bore extends may be equal to or less than the length of the body. In some embodiments, the hole extends through the body a predetermined length shorter than the body, and in such embodiments a shoulder is provided along the inner surface of the hole, with the further axial direction of shoulder 132a. can function as an abutting portion that prevents the movement of the

FIG. 4C illustrates an example gauge 402, according to one or more embodiments. In the illustrated embodiment, gauge 402 includes a body 410 that is open at first end 404 thereof. As shown, body 410 includes a hole 412 extending through the body from first end 404 toward second end 414 , although second end 414 is located in the embodiment shown. is not open. The hole 412 thus extends through the first end 404 and into the body 410 but stops at a location 416 sandwiched between the first and second ends 404 , 414 . As shown, bore 412 includes an internal threaded bore 406 that extends into body 410 and terminates in abutment 418 . Holes 412 also extend from abutment 418 into body 410 such that abutment 418 is sandwiched between internal threaded hole 406 and internal unthreaded hole 420 . is shown to include an internal hole 420 that has not been cut. In the illustrated embodiment, the abutment 418 is provided as a shoulder that reduces the diameter of the internal unthreaded bore 420 relative to the internal threaded bore 406 . However, in other embodiments, the abutment 418 is provided as a protrusion, annulus, or other structure that may or may not affect the diameter of the internal unthreaded bore 420. good too. Here, an internal threaded bore 406 is located adjacent the first end 404 of the body 410 and arranged to mate with the threads 408 of the open end 112 a of the sleeve 112 . An internal unthreaded bore 420 containing a screw 422 is positioned to be sandwiched between the abutment portion 418 and the second end 414 of the body 410 .

In use, a technician places first end 404 of gauge 402 in first direction D1 opposite open end 112a of sleeve 112 and inserts its internal threaded hole 406 into the hole. is screwed over the threads 408 in the open end 112a of the sleeve 112 . The technician then inserts the heating tube 114 into the bottom open end 112b of the sleeve 112 in the second direction D2. After placing the heating tube 114 within the sleeve 112, the technician clamps the heating tube 114 to a location at the lower end of the sleeve 112, eg, via nut assembly 136b. The technician then removes the gauge 402 and clamps the heating tube 114 in place on the upper end of the sleeve 112, for example via the nut assembly 136a. A technician can then tighten the heating tube 114 in place.

As mentioned above, the test method is run in two parts. In the first part, test rig 100 is used to generate thermal oxide deposits. In the second part, specialized equipment is used to quantify the thermal oxide deposits produced during the first part. FIG. 5 illustrates a sequence of functions 502 performed by rig 100 during a first portion of a test method for producing thermal oxide deposits, according to one or more embodiments. As shown, the set of functions 502 includes an aeration step or procedure 504, a pre-filtration step or procedure 508, a busbar cooling step or procedure, a tube heating step or procedure 510, and a differential pressure measurement step or procedure 512. Cooling of the busbars will be discussed in greater detail below.

A jet fuel sample S is a fixed amount of jet fuel and is stored in a sample container 102 . Rig 100 utilizes pump system 506 to transfer or pump fuel sample S from sample container 102 through measuring section 110 across heating tube 114 and ultimately to waste container 104 at a constant flow rate. The jet fuel sample S degrades on the heated heating tube 114 and can form thermal oxide deposits that appear as a visible film thereon. Additionally, degraded material from the jet fuel sample S may flow downstream from the heated tube 114 and be trapped in the test filter 120, for example.

Accordingly, fuel sample S is prepared by first aerating or saturating with dry air via aeration procedure 504 . After the aeration procedure 504, the rig 100 subjects the fuel sample S to a pre-filtration step 508, for example by pumping the fuel sample S through a paper membrane. In one embodiment, the paper membrane of pre-filtration step 508 is a 0.45 μm filtration membrane. The pump system 506 then conveys the fuel sample S at a constant volumetric flow rate through the fuel inlet 116 of the sleeve 112 to the measuring portion 110 . The fuel sample S flows through the measuring section 110 between the inner wall of the sleeve 112 and the outer wall of the heating tube 114 and exits the sleeve 112 through the fuel outlet 118 of the sleeve 112 . After exiting sleeve 112 , fuel sample S passes through test filter 120 and rig 100 performs differential pressure measurement step 512 .

In the illustrated embodiment, the differential pressure measurement step 512 performs a differential pressure measurement between the pressure in the line upstream of the test filter (P+) and the pressure in the line downstream of the test filter (P-). estimating the blockage rate of the test filter 120 by . The percent plugging across the test filter 120, hereinafter referred to as differential pressure drop (ΔP), is measured by a mercury manometer or electronic transducer. Rig 100 may also include a differential bypass line having a valve that may be selectively opened and closed to facilitate flow of fuel sample S through the bypass line. For example, if the differential pressure drop ΔP across the test filter 120 begins to rise sharply (and the technician wishes to run the entire test procedure), the differential bypass line is You can open the valve.

As briefly mentioned above, the test method requires a technician to prepare the fuel sample S through the aeration procedure 504 . More specifically, prior to performing the test method, the fuel sample S contained in the sample container 102 was injected with dry air for 6 minutes at a flow rate of 1.5 liters (“L”) per minute (min). , this test method mandates the technician. However, existing instruments utilize manual airflow adjustments that can affect and affect the accuracy and reproducibility of test method results. FIG. 6A shows an exemplary aeration procedure 504 that includes several manual aeration sequences 602 utilized by existing equipment. As shown, the manual aeration sequence 602 (sometimes referred to as the aeration phase) begins by providing Air A at atmospheric pressure and then through pump 606 at a flow rate of 1.5 L/min. Air A is pumped through filter 604 . Pre-filtered air A is then subjected to a drying process, for example, via air desiccant 608 and humidity sensor 610 which together dry and measure the amount of moisture present in air A. Air A is then directed to a variable area flow meter 612 which is manually adjusted to ensure that Air A is injected into the sample container 102 at the desired flow rate to ensure proper aeration. In the illustrated embodiment, air A is directed from the variable area flow meter 610 to a diffuser 614 located within the sample container 102, which diffuser 614, as specified in the test method, is in contact with the eye. It may be a rough 12 millimeter (“mm”) borosilicate glass diffuser tube. It will be appreciated that aeration of the fuel sample S results in fumes being expelled from the system via the ventilation system. However, the aeration sequence 602 is manual and the test method results depend on the skill of the technician and the operation of the variable area flow meter 612 and may or may not be accurate.

FIG. 6B shows an alternative aeration sequence 622 for automatically controlling airflow during a test method, according to one or more embodiments. Similar to manual aeration sequence 602 , aeration sequence 622 also involves the use of filter 604 , pump 606 , air desiccant 608 , humidity sensor 610 , and diffuser 614 located within sample container 102 . However, because the aeration sequence 622 is performed automatically, no manual intervention or adjustment is required to maintain the desired flow rate, thereby ensuring that the test method defined flow rate is maintained throughout the aeration sequence 622. Ensure that it is available/secured. Thus, in the illustrated embodiment, the aeration sequence 622 utilizes an electronic flow meter 624 (instead of the variable area flow meter 610 of the manual aeration sequence 602), and the pump 606 has controls associated with the electronic flow meter 624. A loop or controller 626 is included to maintain a desired flow rate as air A is pumped through air desiccant 608 and humidity sensor 610 during at least a portion of automatically controlled aeration sequence 622 . In one embodiment, the controller 626 is a servo control using pulse width modulation to regulate the operation of the pump 606 and the electronic flow meter 624 so that the fuel sample S is properly aerated as prescribed. . However, in other embodiments, the automatic airflow control of the aeration sequence 622 may be configured differently, for example, the pump 606 and electronic flow meter 624 may include multiple sensors and use logic to pre-determine may be maintained at a flow rate of

As described above, the pump system 506 transports the fuel sample S from the sample container 102 through the measuring portion 110, across the heating tube 114, and finally to the waste container 104 at a constant flow rate. In fact, the test method stipulates that the fuel sample S must flow at a flow rate of 3 mL/min under a pressure of 500 pounds per square inch ("PSI"). This low flow rate, together with the variability of the mechanical properties of the fuel sample S (i.e. viscosity, density, etc.) hinders the ability to reliably use conventional pumping systems (i.e. membrane pumps, piston pumps, etc.) This can adversely affect the accuracy of test method results. Additionally, the flow rate can also affect the quality of the thermal oxide deposits that form on the heating tubes 114 . For example, a period of low flow followed by an abrupt flow increase with a large temperature gradient can induce axisymmetric instabilities near the hot surface (i.e., Taylor column-type toroidal vortices) and these 'local eddies' may act to remove a thin layer of thermal oxide deposits (formed thereon) from the heating tube 114 while making the overall flow through the heating tube 114 less turbulent. Therefore, the pump system 506 utilized should provide a smooth and steady flow rate so as not to damage the thermal oxide deposits that form.

In the past, the conventional pump system 506 included a single syringe so that the entire fuel volume (ie, the fuel sample S required for testing) was placed in a single syringe. However, this generation of devices suffered from many problems related to the size of the syringe, as well as its handling and leakage. For example, if a single syringe having a volume less than the total volume of sample fuel S required for the test method is utilized, flow pauses and stutters are inevitable during aspiration. Other conventional pump systems 506 utilized high performance liquid chromatography (“HPLC”) pumps with a pair of pistons. However, HPLC pumps are unsatisfactory because they produce a small discontinuity in flow at the end of each piston cycle. Additionally, HPLC pumps are expensive to purchase and maintain.

In one embodiment, the pump system 506 has a pair of syringe configurations that ensure a steady flow of the fuel sample S regardless of the mechanical properties of the fuel sample S. FIG. 7 illustrates a pump system 702 that utilizes a paired syringe/piston configuration, according to one or more embodiments. As shown, pump system 702 includes two syringe or piston assemblies 704, 706 actuated by a pair of motors 708, 710, respectively. Accordingly, first motor 708 operates to drive first syringe assembly 704 while second motor 710 operates to drive second syringe assembly 706 .

In the illustrated embodiment, each syringe assembly 704, 706 includes a barrel 712 that is hollow and defines an interior volume 714 into which a fuel sample S is pumped. Barrel 712 includes a tip 716 at a first end of barrel 712 and an open end 718 directed opposite tip 716 at a second end of barrel 712 . Each syringe assembly 704, 706 also includes a plunger (or piston) 720 extending through its open end 718 into the interior volume 714 of the barrel to fill the interior volume 714 with a fuel sample S. It can be slid inside to increase or decrease the amount. Piston 720 includes a head portion 722 and a shaft 724 coupled to the rear surface of head portion 722 . Head portion 722 is dimensioned to fit within interior volume 714 such that its outer edge or circumference abuts the inner wall of barrel 712 , thereby forming a seal between the outer circumference of head portion 722 and the inner wall of barrel 712 . , thereby preventing fuel sample S from leaking or flowing out of open end 718 of barrel 712 . Axle 724 extends through interior volume 714 in a direction away from the rear face of head portion 722 and exits barrel 712 through open end 718 .

In addition, shaft 724 includes an end 726 disposed opposite head 722 and operably engaged with one of motors 708,710. In one embodiment, motors 708 , 710 are stepper motors each including a ball screw transmission 728 that rotates to drive piston 720 . In such an embodiment, a ball screw transmission 728 is coupled to end 726 of shaft 724 and drives plunger head 722 relative to barrel 712 , thereby changing the dimensions of interior volume 714 . The feedrate of piston 720 is applied by motors 708 , 710 via ball screw transmission 728 .

Each syringe assembly 704 , 706 also includes a pair of check valves 730 , 732 for controlling the flow of fuel sample S into and out of the interior volume 714 of barrel 712 . Here, check valves 730 , 732 are positioned at each distal end 716 . A first check valve 730 is disposed on an input line 734 that fluidly interconnects the sample container 102 to the interior volume 714 of the barrel 712 to allow fuel sample S from the sample container 102 to the interior volume 714 of the barrel 712 to flow. flow and prevent reverse flow. Similarly, a check valve 732 is disposed on a fluid output line 736 that fluidly interconnects the interior volume 714 to other downstream systems, such as those utilized in the prefiltration step 508 , to remove the fluid from the barrel 712 . It allows flow to such downstream devices and prevents reverse flow.

The syringe assemblies 704, 706 operate in an alternating firing sequence. For example, when the first syringe assembly 704 draws the fuel sample S into the relevant barrel 712 (i.e., the aspiration phase), the second syringe assembly 706 expels the fuel sample S from the relevant barrel 712 ( i.e. the ejection stage). With this configuration, one of the syringe assemblies 704, 706 is always performing an ejection step, thereby providing a fuel sample S to the downstream device at a constant flow rate, as defined by the test method. We guarantee that.

Fuel sample S is drawn into and expelled out of barrel 712 via the axial movement of piston 720 back and forth within barrel 712 . As the piston 720 is pulled from the first syringe assembly 704 in the first direction X1 at a constant velocity, a volume of fuel sample S is aspirated from the sample container 102 . At the same time, piston 720 of second syringe assembly 706 is forced into barrel 712 at a constant velocity. When the piston 720 is pushed into the second syringe assembly 706 , the fuel sample S within the respective barrel 712 is expelled at a flow rate that depends on the diameter of the head portion 722 and the rate at which it is displaced within the internal volume 714 . As described above, the pair of check valves 730, 732 ensure alternate actuation of the aspiration and ejection phases; in some embodiments the pair of check valves 730, 732 are active valves; In this embodiment, the pair of check valves 730, 732 are passive valves.

The pump system 702 pumps the fuel sample S while switching from one syringe assembly 704, 706 to the other with imperceptible flow fluctuations. This accelerates one piston 720 at the beginning of its stroke at the bottom of barrel 712 (i.e., near open end 718) such that piston 720 moves toward tip 716 in first direction X2. , simultaneously decelerating the second piston 720 as it nears the end of its stroke (ie, near tip 716). Thus, deceleration of the piston 720 on one side (eg, the first syringe assembly 704 at the end of the cycle) is complemented by acceleration of the piston 720 on the other side (eg, the second syringe assembly 706) and vice versa. The same is true for This phasing is provided so that the sum of the velocities of the pistons 720 of the first and second syringe assemblies 704, 706 is always equal to the nominal feed rate, thereby providing a Ensure a constant flow rate. In the illustrated embodiment, the internal volume 714 of each barrel 712 is 5 mL and the fuel sample S flow rate is 3 mL/min. In the illustrated embodiment, the switching time from one syringe assembly 704, 706 to the other is approximately 20% of the total cycle time, thereby eliminating any flow fluctuations.

As the fuel sample S is pumped through the measurement section 110, a steady current is applied to the heating tube 114 via the busbars 122a, 122b to generate heat depending on the temperature and/or quality of the fuel sample utilized in the particular test. Oxide deposits may form on heating tube 114 as a visible film. Heating tube 114 is maintained at a relatively high temperature, eg, 260° C., although this temperature may be higher or lower depending on the application. The current applied to heating tube 114 is controlled to maintain a stable temperature at the point of measurement.

FIG. 8 shows a conventional heating system 802 for heating the heating tubes 114 via bus bars 122a, 122b. As shown, a conventional heating system 802 includes a power supply 804, a control system 806, a thermocouple 124 measuring a hot spot 808 at a point P on the heating tube 114, and a pair of bus bars 122a securing the heating tube 114. , 122b. Heating tube 114 is resistively heated by the conductance of a high amperage, low voltage current flowing through heating tube 114 from power supply 804, resulting in heating tube 114 having the illustrated thermal profile. Here, the measuring point P of the thermocouple 124 is located inside the heating tube 114 and is determined by the length of the shoulders 132a and 132b of the heating tube 114. In this test method, the length is 39 mm. This 39 mm point is therefore at the hottest region (ie, hot spot 808) of the heating tube 114 utilized in the test method.

In the illustrated embodiment, the busbars 122a, 122b are relatively heavy and water-cooled, resulting in relatively minimal temperature rise when current is applied. Control system 806 functions as an indicator and/or controller. For example, the control system 806 may automatically control the temperature and vary the power supplied from the power supply 804 as needed to provide a stable heat source to the busbars 122a, 122b and the heating tubes 114. . Accordingly, the heating system 802 may be utilized to maintain a target temperature, eg, 260° C., as defined by the test method. Alternatively, the control system 806 may instead provide manual operation, thereby providing only a temperature readout so that the technician can manually adjust the temperature as needed.

The thermal profile of heating tube 114, and thus the location of hotspot 808 thereon, can be influenced by many factors. These factors include the thermal properties of the fuel sample S, the temperature of the busbars 122a, 122b, and the temperature difference (ΔT) between the busbars 122a, 122b. Additionally, the ability to control the thermal profile of the heating tube 114 can improve test method results and their reproducibility. However, conventional instruments do not include a control system that allows for fine tuning of the thermal profile of heating tube 114 . For example, existing equipment includes cooling systems that remove heat applied to the busbars 122a, 122b by conduction from the hot heating tubes 114, and engineers have control over these existing cooling systems. The thermal profile of heating tube 114 cannot be optimized.

The busbars 122a, 122b of the existing rig 100 are cooled via a water cooling system that circulates water along a single path that flows through each busbar 122a, 122b. Water may be provided from an external source, such as a laboratory sink, or existing equipment may circulate water by including an internally circulated and radiator cooled water system. FIG. 9A is a diagram showing how an existing busbar water cooling system 902 works, and FIG. 9B shows an exemplary internal cooling system 904 that may be incorporated into existing equipment. However, these existing systems circulate the liquid through busbars 122a, 122b and then through a heat exchanger 908 associated with a fan 910 that cools the liquid by blowing air at ambient temperature, a liquid pump 906. and is not temperature controlled.

During operation of the existing instrument, an initially unheated fuel sample S is introduced into the sleeve 112 near the lower busbar 122b and heated along the length of the heating tube 114 as it flows upwardly. , exit the sleeve 112 near the hot upper busbar 122a. However, while a fuel sample S consisting of a fuel with good heat transfer properties reduces the temperature of the lower busbar 122b, such a fuel sample S does not have the same effect on the upper busbar 122a. This in turn affects the thermal profile of the heating tube 114 by, for example, distorting the size of the hotspot 808 and/or moving the hottest point P closer to the upper shoulder 132a. give. Because the temperature control system 806 is designed to take temperature measurements at a single point, assumed to be the hottest point P on the heating tube 114, these effects adversely affect the results of the test method. can affect However, if the thermal profile distorts and the hottest point P shifts upward along the heating tube 114, the temperature control system 806 no longer measures the hottest point P and is therefore inaccurate. results. Further, when performing successive tests, e.g., when several tests are performed in rapid succession, the cooling fluid becomes warmer and the thermal condition of the heating tube 114 changes to the thermal condition of each subsequent test. is no longer identical to

FIG. 10 illustrates a temperature system 1002 for controlling temperature within busbars 122a, 122b, in accordance with one or more embodiments. The temperature system 1002 individually controls the temperature of each of the busbars 122a, 122b such that the temperature of each is controlled independently of each other, thereby maintaining the thermal profile of the heating tube 114 constant. In this manner, the temperature difference (ΔT) between busbars 122a, 122b may be minimized and/or fixed, or set to a desired value. Furthermore, by fixing the temperature difference (ΔT) between the upper busbar 122a and the lower busbar 122b, the temperature system 1002 may also limit the effects of variations in the thermal properties of the fuel sample S being tested. .

Temperature system 1002 maintains a constant thermal profile of heating tube 114 as a function of test method temperature (eg, 260° C. for some test methods). Therefore, in order to perfectly control the temperature of each busbar 122a, 122b and ensure perfectly correlated results, their thermal profiles are based on typical thermal profiles obtained from existing equipment. assumed to be The reproduced profile is an image of a test run under normal ambient temperature and discontinuous test conditions. Furthermore, if the test method protocol were to change or improve in the future, e.g., requiring that the upper busbar 122a and the lower busbar 122b maintain the same temperature (e.g., 35[deg.] C.), the temperature system 1002 would , meet these new requirements, but existing equipment that utilizes liquid circulation cannot meet those new requirements.

As shown, temperature system 1002 includes an upper busbar subsystem 1004 and a lower busbar subsystem 1006 that control the temperature of upper busbar 122a and lower busbar 122b, respectively. Each busbar subsystem 1004, 1006 includes a cooling module 1010, a heat sink 1012, a controller 1014, a forced convection device 1016, and a thermocouple 1018 that measures the temperature of the respective busbar 122a, 122b. In the illustrated embodiment, the cooling module 1010 is a Peltier device and the forced convection device 1016 is a fan, although other cooling modules 1010 and/or forced convection devices 1016 may be utilized without departing from this disclosure. good too. It will be appreciated that each busbar subsystem 1004, 1006 includes a separate controller 1014 and components so that the heat extracted from the busbars 122a, 122b by the respective heat pipes 1008 can be individually regulated.

The cooling module 1010 is powered such that the amount of thermal energy transferred from the busbars 122a, 122b to the respective heat sinks 1012 is controlled based on temperature measurements performed on each of the busbars 122a, 122b. be done. The measurement points used for these temperature measurements are arranged on the busbars 122a, 122b at points close to the connection with the heating tube 114, for example, at the same locations as the measurement points provided on the busbars of existing equipment. can be placed respectively.

Busbars 122a, 122b may have a shape to optimize heat transfer. For example, the outer profile or shape 1019 of the busbars 122a, 122b may be formed to use the entire heat exchange surface of the cooling module 1010 as shown. Also, in the illustrated embodiment, each bus bar 122a, 122b includes a base 1020 and a bore 1022 extending inwardly therefrom toward a tapered end 1024 that retains or secures the heating tube 114. , the heat pipes 1008 are inserted into the holes 1022 of the busbars 122a, 122b. Because the heat pipe 1008 has a higher thermal conductivity than the busbars 122a, 122b (which may be made of brass, for example), heat is more efficiently transferred from one end of each busbar 122a, 122b to the other. be. The temperature difference (ΔT) between the measurement points (i.e., the thermocouple 1018 measurement points) and the contact area of the cold surface of the cooling module 1010 can be reduced, thereby improving the efficiency of the cooling system 1002 and the response time of the control loop. is improved. Thus, the temperature system 1002 provides independent thermal control of the individual busbars 122a, 122b while eliminating ambient temperature effects compared to cooling means based solely on heat exchange with the ambient temperature.

FIG. 11A shows a clamping system 1102 utilized to secure the lower shoulder 132b of heating tube 114 (within sleeve 112) to lower busbar 122b. As shown, the clamping system 1102 includes a plate 1104 movably positioned adjacent an end face 1106 of the lower busbar 122b to clamp the underside of the heating tube 114 positioned within the lower busbar 122b. is arranged to clamp or grip the shoulder 132b of the . Clamping system 1102 further includes a pair of screws 1108 that extend through an outer surface 1110 and an inner surface (hidden from view of the figure) of plate 1104 and into end surface 1106 of lower busbar 122b. It will be appreciated that by tightening or loosening screws 1108, a technician can tighten or press plate 1104 against lower busbar 122b. Thus, the lower shoulder 132b of the heating tube 114 (fixed within the sleeve 112) is positioned between the inner surface (hidden from view of the figure) of the plate 1104 and the end face 1106 of the lower busbar 122b. The technician can then tighten or loosen screw 1108 to secure or remove measuring portion 110 . In some embodiments, either or both the inner surface (hidden from view of the figure) of plate 1104 and the end surface 1106 of lower bus bar 122b are adapted to receive lower shoulder 132b of heating tube 114. It is formed. Additionally, screw 1108 may include a lever 1112 extending therefrom to facilitate tightening and loosening thereof. Although not shown, it will be appreciated that a clamping system 1102 for securing/unlocking the upper shoulder 132a thereto is also located on the upper busbar 122a.

To attach or detach the sleeve 112 and heating tube 114 assembly (i.e., the measuring portion 110) from the lower busbar 122b, the technician will need to ensure that the plate 1104 engages the lower shoulder 132b of the heating tube 114. The plate 1104 must be moved so as not to disturb the position on the receiving end face 1106 . One method is for the technician to completely remove one screw 1108 and then loosen another screw 1108 to allow the plate 1104 to pivot about the (remaining) screw 1108, thereby , the lower shoulder 132b within the end face 1106 of the lower busbar 122b without hindrance. Alternatively, the technician may remove both screws 1108 to completely remove the plate 1104 from the end face 1106 of the lower busbar 122b to install or remove the measuring portion 110. FIG. Although not described, it will be appreciated that the operations of clamping system 1102 described above may be similarly applied to upper busbar 122a to secure/unlock upper shoulder 132a thereto.

However, alternative clamping systems may be utilized that do not require two screws and provide improved electrical and/or thermal contact between shoulders 132a, 132b and busbars 122a, 122b. For example, FIG. 11B illustrates a clamping system 1120 according to one or more embodiments. As detailed below, the illustrated clamping system 1120 utilizes a single screw that can be removed to attach or detach the heating tube 114 to provide improved thermal and electrical contact. obtain. Although the clamping system 1120 of FIG. 11B may be utilized for one or both of the upper busbar 122a and the lower busbar 122b, hereafter a single clamping system that may be utilized as either the upper or lower busbars 122a, 122b. Application to an unspecified bus bar 122 will be described.

As shown, the busbars 122 utilized in clamping system 1120 diverge at tapered ends 1024 . Accordingly, tapered end 1024 of busbar 122 includes a pair of tines or projections 1122a, 1122b extending away from base 1020 of busbar 122 therefrom. A pair of protrusions 1122a, 1122b define a recess or gap 1124 therebetween. Here, gap 1124 is dimensioned such that shoulders 132a, 132b of heating tube 114 may be inserted or retracted therethrough as described below. Additionally, the tapered ends 1024 may be hollow so as to define threaded holes 1126 that extend into the busbar 122 at least the length of the projections 1122a, 1122b.

In the illustrated embodiment, the clamping system 1120 further includes a screw 1128 having a threaded portion 1130 received within and mating with a threaded hole 1126 of the busbar 122 . The clamping system 1120 also includes a plate 1132 positioned within the gap 1124 between the pair of projections 1122a, 1122b, the plate 1132 sliding between the projections 1122a, 1122b to clamp the shoulder 132a of the heating tube 114. , 132b of the busbar 122 toward and away from the inner surface 1134 thereof. In operation, one of the shoulders 132a, 132b is positioned adjacent the inner surface 1134 of the busbar 122 so that the screw 1128 can be rotated to move its threaded portion 1130 into and out of the threaded hole 1126. and further drives the plate 1132 toward and away from the inner surface 1134, thereby tightening or unclamping one of the shoulders 132a, 132b disposed therebetween. When screw 1128 and plate 1132 are withdrawn from tapered end 1024 of busbar 122, the clearance is unobstructed and shoulders 132a, 132b of heating tube 114 can be inserted or withdrawn. In the illustrated embodiment, plate 1132 and inner surface 1134 each include bearing surfaces 1132', 1134' configured to receive shoulders 132a, 132b.

Also in the illustrated embodiment, the screw 1128 is hollow and includes a bore 1136 having a smaller diameter portion 1137a and a larger diameter portion 1137b, and the plate 1132 is hollow and defines a bore 1140 coaxial with the bore 1136 of the screw 1128. including axis 1138 that forms. As shown, the shaft 1138 and its hole 1140 extend from the plate 1132 away from the base 1020 of the busbar 122 through the small diameter portion 1137a of the hole 1136 of the screw 1128 to the large diameter portion 1137b. .

A locking device 1142 may be utilized to limit or inhibit the amount of axial movement of plate 1132 within gap 1124 relative to screw 1128 while allowing rotation of screw 1128 relative to plate 1128 . Fixture 1142 is secured within hole 1140 of plate 1132 . Further, the fixing device 1142 floats within the large diameter portion 1137b of the hole 1136 of the screw 1128 and abuts a shoulder 1146 within the hole 1136 of the screw 1128 when the screw 1128 is pulled out of the hole 1126 of the busbar 122. 1144 (ie, a flange positioned between the small diameter portion 1137a and the large diameter portion 1137b). Also, shaft 1138 of plate 1132 is fully withdrawn from hole 1136 of screw 1128 through the interaction of flange 1144 and shoulder 1146 while allowing relative rotation between plate 1132 and screw 1128. A plate 1132 may be attached to the screw 1128 to prevent it from slipping. Thus, attempting to withdraw the screw 1128 from the threaded hole 1126 of the busbar 122 causes the plate 1132 (attached to the fixture 1142) to be pulled axially away from the base 1020 of the busbar 122 by the (rotating) screw 1128. In other words, rotation of screw 1128 translates into axial displacement of plate 1132 within gap 1124 . Accordingly, the plate 1132 is carried (or withdrawn) by the screws 1128 to remove the plate 1132 from the tapered end 1024 of the busbar 124 so that the shoulders 132a, 132b of the heating tube 114 can be assembled or removed from the gap 1124. Removal exposes gap 1124 , thereby facilitating removal of heating tube 114 from busbar 122 .

In some embodiments, as described above, the busbar 122 is positioned above or below the busbar 122 and a pair of recesses 1018a, 1018b positioned to receive one of the thermocouples 1018 of the temperature system 1002. can have one or both of

Accordingly, the disclosed system and method are well adapted to attain the ends and advantages mentioned as well as those inherent therein. The specific embodiments disclosed above are merely exemplary, as the teachings of the present disclosure can be modified and implemented in different but equivalent ways, which will be apparent to those skilled in the art having the benefit of the teachings herein. Absent. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular exemplary embodiments disclosed above may be altered, combined or modified and all such variations are considered within the scope of the present disclosure. The systems and methods illustratively disclosed herein may be suitably practiced in the absence of any element not specifically disclosed herein and/or any element disclosed herein. can. Although structures and methods are described in terms of "comprising," "having," or "including" various components or steps, structures and methods "consist essentially of" various components and steps. or "consisting of". All numbers and ranges disclosed above can vary to some extent. Whenever a numerical range with a lower and upper limit is disclosed, any number and any inclusive range within that range are specifically disclosed. In particular, all value ranges disclosed herein (of the form "from about a to about b", or equivalently "from about a to b", or equivalently "from about a to b") are It should be understood that all numbers and ranges are included in the broader range of values. Also, terms in the claims have their plain and ordinary meanings unless explicitly and unambiguously defined by the patentee. Moreover, as used in the claims, the indefinite articles "a" or "an" are defined herein to mean one or more of the elements it introduces. In the event of conflict in the usage of a word or term in this specification and one or more patents or other documents that may be incorporated herein by reference, the definitions consistent with this specification shall control.

The use of directional terms such as up, down, above, below, above, below, left, right, etc., are used in connection with the exemplary embodiments shown in the figures, and are used to refer to "upwards" or "upwards." "Direction" indicates toward the top of the corresponding figure, and "downward" or "downward" indicates toward the bottom of the corresponding figure.

As used herein, the phrase "at least one" preceding a series of items, with the terms "and" or "or" separating any of the items, each member of the list ( That is, it qualifies the list as a whole, rather than each item). The phrase "at least one" is allowed to mean including any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. . By way of example, the phrases "at least one of A, B, and C" or "at least one of A, B, or C" refer to only A, only B, or only C; , and any combination of C; and/or at least one of each of A, B, C.

Claims (21)

A temperature system for independently controlling the temperature of busbars to improve the thermal profile of heating tubes in a thermal oxidation rig, said temperature system comprising:
a heat sink positioned proximate a base of the busbar to secure the busbar to the thermal oxidation rig;
a cooling element interposed between the heat sink and the base of the busbar;
a forced convection device;
a thermocouple positioned at the end of the busbar opposite the base proximate the heating tube, the thermocouple measuring the temperature of the busbar;
a controller associated with the cooling element and the forced convection device, the controller controlling the cooling element and the forced convection device based on the temperature measured by the thermocouple. , temperature system. 2. The temperature system of claim 1, wherein the busbar includes holes extending from the base for receiving heat pipes. A thermal oxidation rig for analyzing fuel samples, said thermal oxidation rig comprising:
a measuring section having a sleeve and heating tube assembly supported by a pair of busbars;
the sleeve and heating tube assemblies are secured within clamping assemblies on the respective busbars;
the sleeve being hollow and open at opposite ends;
said heating tube secured within said sleeve and hermetically sealed;
a fuel inlet and a fuel outlet positioned on the sleeve between open ends;
and the temperature system of claim 1 for individually controlling the temperature of the busbars to improve the thermal profile of the heating tubes within the thermal oxidation rig. 4. The thermal oxidation rig of claim 3, wherein said busbar includes holes extending from said base for receiving heat pipes. 4. The thermal oxidation rig of claim 3, wherein the thermal oxidation rig comprises:
further comprising a pumping system for conveying a fuel sample from a sample container through the measuring portion to the fuel inlet, the pumping system comprising:
first and second syringe assemblies, each syringe assembly comprising a hollow barrel defining a volume for holding said fuel sample, a tip located at an upper end of said barrel; an open end located at the lower end of the barrel, each syringe assembly having an inlet valve and an outlet valve;
a pair of pistons each arranged to slide within a volume of said one barrel, each piston extending into said volume through said open end of said barrel; a pair of pistons having shafts connected to a head portion that contacts the inner wall of the hollow barrel so as to seal the volume against the open end of the barrel;
A pair of motors, each motor engaged with one of the pistons and independently controlled so that the flow rate of the fuel sample is kept constant, each motor simultaneously controlling the piston a pair of motors that control the stroke of the appropriate pistons to accelerate and decelerate. 6. The thermal oxidation rig of claim 5, wherein the pump system comprises:
A thermal oxidation rig, further comprising a common inlet line feeding both said inlet valve of said first syringe assembly and said inlet valve of said second syringe assembly. 7. The thermal oxidation rig of claim 6, wherein said common inlet line is connected to a sample vessel holding said fuel sample. 6. The thermal oxidation rig of claim 5, wherein the pump system comprises:
A thermal oxidation rig, further comprising a common outlet line for receiving from both the outlet valve of the first syringe assembly and the outlet valve of the second syringe assembly. 9. The thermal oxidation rig of claim 8, wherein said fuel sample is conveyed through said common exit line at a constant flow rate. 6. The thermal oxidation rig of claim 5, wherein the pump system comprises:
A thermal oxidation rig further comprising a pair of ball screw transmissions, each ball screw transmission being interposed between the respective motor and the piston. 4. The thermal oxidation rig of claim 3, wherein the thermal oxidation rig comprises:
Equipped with a gauge for positioning the heating tube within the sleeve,
The gauge comprises a body having first and second ends and a bore extending a predetermined length from the first end into the interior of the body, the bore extending through the sleeve. Having a diameter sized to receive the open end, the heating tube includes a pair of shoulders flanking a reduced diameter portion, the pair of shoulders oriented away from the lip portion relative to the reduced diameter portion. and said one shoulder extends through said sleeve in said lengthwise direction of said bore such that said lip is positioned proximate to the outlet of said sleeve. and a thermal oxidation rig. 12. The thermal oxidation rig of claim 11, wherein said hole in said gauge comprises:
A thermal oxidation rig extending from said first end a predetermined length shorter than said body. 12. The thermal oxidation rig of claim 11, wherein the gauge comprises:
A thermal oxidation rig comprising a shoulder radially disposed along said hole at a distance equal to said length from said first end. 12. The thermal oxidation rig of claim 11, wherein the hole comprises:
A thermal oxidation rig, wherein said body extends from said first end to said second end. 12. The thermal oxidation rig of claim 11, wherein a portion of said bore proximate said first end of said body is threaded. 4. The thermal oxidation rig of claim 3, wherein the thermal oxidation rig comprises:
an aeration system for aerating the fuel sample in the sample container, the aeration system comprising:
a pump;
a flow meter that measures the air flow generated by the pump and injected into the sample container;
A thermal oxidation rig, wherein said pump further comprises a controller associated with said flow meter for automatically maintaining said airflow at a constant flow rate through a control loop. 17. The thermal oxidation rig of claim 16, wherein the aeration system comprises:
A thermal oxidation rig, further comprising an air desiccant to remove moisture from said airflow. 18. The thermal oxidation rig of claim 17, wherein the aeration system comprises:
A thermal oxidation rig, further comprising a humidity sensor positioned to sample the airflow passing through the air desiccant. 17. The thermal oxidation rig of claim 16, wherein said sample vessel of said aeration system comprises:
A thermal oxidation rig, further comprising a diffuser positioned in said sample container. 17. The thermal oxidation rig of claim 16 , wherein the aeration system comprises:
A thermal oxidation rig, further comprising a filter for filtering said airflow prior to passing through said pump. 4. The thermal oxidation rig of claim 3, wherein the assembly for clamping the heating tube to the busbar comprises:
a hole extending toward an end of the busbar and terminating at an inner surface of the busbar;
a pair of projections extending from the inner surface of the busbar to the end, the projections defining a gap extending with the hole;
a plate arranged to slide axially within said gap;
a screw disposed within the hole and engaged with the plate;
A thermal oxidation rig, wherein rotation of said screw translates said plate in said axial direction.

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